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//! Stopping the server when it is asked to, rather than when it is killed.
//!
//! Only `ctrl_c` was awaited, so `SIGTERM` -- what `docker stop`, Kubernetes
//! and systemd all send -- reached no handler. As PID 1 in a container the
//! kernel applies no default action either, so the signal was silently
//! discarded and every stop waited out the full grace period before a
//! `SIGKILL`, severing any in-flight stream at the timeout rather than allowing
//! it to finish (issue #334).
//!
//! Split from `main.rs` to keep that file within the repository's 1000-line
//! limit.
/// A shutdown notice that every listener can await.
///
/// The signal has to reach four listeners -- HTTP, HTTPS, the admin UI and the
/// unix socket -- and a future can only be awaited once, so it fans out over a
/// broadcast channel rather than being consumed by whichever listener got it
/// first (issue #334).
#[derive(Clone)]
pub struct Shutdown(tokio::sync::broadcast::Sender<()>);
impl Shutdown {
/// Start listening for the signals that ask this process to stop.
pub fn listening() -> Self {
let (sender, _) = tokio::sync::broadcast::channel(1);
let notifier = sender.clone();
tokio::spawn(async move {
shutdown_signal().await;
// A send fails only when nothing is listening, which means every
// listener has already stopped.
let _ = notifier.send(());
});
Self(sender)
}
/// A future that resolves when the process should stop serving.
pub fn notified(&self) -> impl std::future::Future<Output = ()> + Send + 'static {
let mut receiver = self.0.subscribe();
async move {
// `Err` means the sender is gone, which cannot happen while the
// process is running -- treat it as a shutdown either way rather
// than leaving a listener awaiting a notice that will never come.
let _ = receiver.recv().await;
}
}
}
async fn shutdown_signal() {
let interrupt = async {
if tokio::signal::ctrl_c().await.is_err() {
// A handler that cannot be installed must not take the process
// down with it: the other signal may still arrive, and an
// unstoppable router is worse than one that stops on one signal.
std::future::pending::<()>().await;
}
};
#[cfg(unix)]
let terminate = async {
match tokio::signal::unix::signal(tokio::signal::unix::SignalKind::terminate()) {
Ok(mut signal) => {
signal.recv().await;
}
Err(error) => {
tracing::warn!("could not listen for SIGTERM: {error}");
std::future::pending::<()>().await;
}
}
};
#[cfg(not(unix))]
let terminate = std::future::pending::<()>();
let name = tokio::select! {
() = interrupt => "SIGINT",
() = terminate => "SIGTERM",
};
tracing::info!("{name} received; draining in-flight requests before exit");
}